samba - Oct 2012 - Office 2010, location is not trusted in samba 3.6.x

Hi,

Everytime a user opens a excel,word,... document on the share office
complains about the file is beying downloaded from the internet and is not
secure. After a push on the allow or edit button, the user can continue his
work.

I know you can add the UNC location to your trusted sites or location
within internet explorer or office trust center.

When the UNC path is a windows server. There is no warning.
So my question, what is the difference?
I've turned on signing, I can see that the packages are signed between
samba and my windows 7 computer. But this doesn't resolve the problem.

Also using the VFS module streams_xattr is not working.

Is there any solution apart from adding the UNC path as trusted on the
client?